Apparatus for accelerating convective heat transfer between a solid and a gas



Feb. 28, 1956 H s ORR ET AL 2,736,548

APPARATUS FOR ACCELERATING CONVECTIVE HEAT TRANSFER BETWEEN A SOLID ANDA GAS Filed Nov. 14. 1952 4 Sheets-Sheet 1 FIG. 2..

FIELL- lnvenioxs: Han 4w 5 0/5? and flLFFEfi 72/ 4/77,

Feb. 28, 1956- s, ORR ET AL 2,736,548

APPARATUS FOR ACCELERATING CONVECTIVE HEAT TRANSFER BETWEEN A SOLID ANDA GAS Filed Nov. 14. 1952 4 Sheets-Sheet 2 s '44 4 4 #0144420 5 flee0/70 141/7950 75 1/72,

Feb. 28, 1956 H, s; ORR ET AL 2,736,548

APPARATUS FOR ACCELERATING CONVECTIVE HEAT TRANSFER BETWEEN A SOLID ANDA GAS Filed Nov. 14. 1952 4 Sheets-Sheet 5 r Inventors:

Han 4&5 0/92 0/70 415950 7274/72,

Feb. 28, 1956 5; ORR ET AL 2,736,548

APPARATUS FOR ACCELERATING CONVE VE} HEAT TRANSFER BETWEEN A SOLID AN AGAS Filed Nov. 14. 1952 4 Sheets-Sheet 4 FIElCJ- A 2,736,548 IcePatented Feb. 28, 1956 APPARATUS FOR ACCELERATING CONVECTIVE HEATTRANSFER BETWEEN A SOLID AND A GAS Howard S. Orr and Alfred Teplitz,Pittsburgh, Pa., assignors to United States Steel Corporation, acorporation This invention relates to apparatus for acceleratingconvective heat transfer between a solid and a gas adjacent thereto andis particularly adapted for accelerating heat transfer between a gas anda strip passing therethrough.

In a continuous annealing of strip steel it is necessary to cool thestrip within a relatively short time. In so doing the smooth strippasses between smooth parallel water jackets. We have found that thestrip carries with it a large volume of the furnace atmosphere gas, butbecause of the smoothness of both the strip and the water cooled wallsthe gas moves in a streamline manner. Thus, there is no mixing betweenthe various layers of the gas and the rate of heat transfer from thestrip to the gas and from the gas to the cold Walls is small.

We have found that to obtain an increased rate of heat transfer it isnecessary to break up the streamline gas flow and create a turbulentflow condition. Insofar as the stationary surfaces of the water jacketsare concerned this may be easily done by providing projections such asfins upon the walls of the water jackets. Breaking up the boundarysurfaces adjacent the strip presents a more difficult problem sincenothing can be done that might permanently deform the strip.

We have found that by vibrating the strip as it passes between the waterjackets and/or by vibrating the atmospheric gas, not only willturbulence be created in the gas, but the boundary layers of the gaswill be broken up and the heat transfer rate greatly improved.

It is therefore an object of our invention to provide apparatus foraccelerating convective heat transfer between a solid, particularly aflat object of considerable area, and a gas adjacent thereto.

This and other objects will be more apparent after referring to thefollowing specification and attached drawings, in which:

Figure 1 is a schematic vertical view, partly in section, of oneembodiment of our invention;

Figure 2 is a schematic view, similar to that of Figure 1, showing asecond embodiment of our invention;

Figure 3 is a schematic isometric view of a third embodiment of ourinvention showing the vibrating means but omitting the cooling chamber;

Figure 4 is a view, similar to Figure 3, showing another embodiment ofour invention;

Figure 5 is a schematic view, partly in cross section, showing means forvibrating the gas in the cooling chamber;

Figure 6 is an enlarged sectional view showing fins located in thecooling chamber;

Figure 7 is an isometric view showing means for vibrating the gas withinthe cooling chamber;

7 Figure 8 is a view, partly in section, showing the vibrating means ofFigure 7;

Figure 9 is a vertical sectional view of our invention as applied to theannealing of coils of steel strip located within an inner cover;

Figure 10 is an enlarged fragmentary view of the supporting means forthe vibrator;

Figure 11 is a side view of Figure 10;

Figure 12 is an enlarged side view of the supporting plate for thevibrator; and

Figure 13 is an end view of Figure 12.

Referring more particularly to Figure 1 of the drawings, the referencenumeral 2 indicates the cold walls of a water jacket through whichpasses a moving steel strip S which is supported by spaced apart rolls4. Suitable means such as bridle rolls (not shown) may be used to pullthe strip over the rolls 4. A magnetic vibrator 6 is mounted adjacentthe strip at the exit end of the water jacket. The magnetic vibratorconsists of a 60 cycle A. C. electromagnet which becomes magnetized anddemagnetized, thus attracting the strip S 60 times per second to causeit to vibrate rapidly. The vibrator is spaced from the strip a distancesufficient to prevent the strip from actually contacting the vibrator.

Figure 2 shows a second means for vibrating the strip which may be usedwith non-magnetic material as well as with steel strip. In thisembodiment a fluted roll 8 is substituted for each of the rolls 4. Therate at which the strip vibrates depends upon the number of flutes inthe roll, the diameter thereof and the speed at which the strip travels.The amplitude of the vibrations depends upon the depth of the flutes. I

Figure 3 shows another means for vibrating the strip S. In thisembodiment a pair of rolls 10 and 12 are mounted one on each side of thestrip S and are adapted to be rotatedby contacting the strip lightly.The rolls are connected by means of a link 14 at each end thereof. Alink 16 is attached to each endof the roll 10 and extends away from thestrip S with its free end thereof being attached to the arm of a crank18. The shaft 20 of the crank is mounted in suitable stationary bearings21 and is rotated by means of a motor, not shown. The rolls 10 and 12are suspended by means of links 22 and 24, respectively, from shafts 26and 28 which are mounted in suitable stationary bearings 29. Rotation ofthe crank produces an oscillation of the rolls 10 and 12 causing thestrip to vibrate rapidly.

Figure 4 shows still another embodiment of our invention. In thisembodiment the lower roll 4 is mounted in bearings 30 which in turn aremounted on a U-shape frame 32. A suitable electro magnet vibrator 34 ismounted on the frame 32 adjacent each of the bearings 30. The U-shapeframe 32 is pivotally mounted on pins 36. Adjustable stops 38 aremounted adjacent the vertical legs of the U-shape frame to limit theamount of movement of the frame 32 about its pivots. When the vibrators34 are operated the U-shape frame 32 carrying the roll 4 will vibraterapidly about the pins 36 thus causing the strip S to vibrate.

In all instances fins 40 (see Fig. 6) are preferably mounted in thecooling chamber to increase the rate of heat transfer.

In addition to or in place of vibrating the traveling strip theatmosphere in the furnace may be vibrated, thus further increasing therate of heat transfer. As shown in Figure 5 this may be done byproviding a steel core 42 within which is mounted a coil 44 having anopening 46 therein for receiving armature 48. A rubber bumper 50 isprovided on the core 42 in order to prevent the armature 48 fromcontacting the core. A light weight plate 52 is attached to the armature48 and is positioned in the cooling chamber 53 adjacent the strip S. Byconnecting the coil 44 to an A. C. current of volts the plate 52 iscaused to reciprocate rapidly, thus vibrating the gas surrounding thestrip S.

Figures 7 and 8 show another manner in which the atmosphere in thecooling chamber may be vibrated. In this embodiment an opening is madein the Walls of the water jacket 54 and a transition piece 56 is mountedon a flange 58 surrounding the opening. A circular diaphragm 60 ismounted on the outer end of the transition piece. A vibrator 62 ismounted on the diaphragm 60 and is provided with a backing piece 64. Itwill be seen that the transition piece 56 has a substantially constantcross sectional area throughout its length and changes from arectangular shape at the flange 58 to a circular shape at its outer end.Energization of the vibrator 62 causes the atmosphere surrounding thestrip S to vibrate rapidly.

Figures 9 to 13 show the application of our invention to the annealingof coils C of steel strip located within an inner cover 66. A protectiveatmosphere is located within the cover 66 and is circulated through andaround coil C by means of a fan 68 in the usual manner. A pair ofstraight pins 70 are welded to the outside of the inner cover 66 beneatha pair of L-shaped pins 72. A vibrator 74 is mounted on a plate 76having two elongated openings 78 therein which fit over the pins 72. Ifdesired a washer 80 may be welded to the pins 72 to hold the plate 76 ina vertical position. A hook 82 is attached to the upper end of plate '76so that the plate can be placed in position and removed by means of acrane. After the strip has been heated to the desired temperature andwhen the outer cover has been removed the vibrator 74 mounted on theplate 76 is placed over the hooks 72 as shown in Figures 9 and and thevibrator is caused to operate thus vibrating the inner cover 66. Thisincreases the rate of heat transfer from the strip S to the protectiveatmosphere into the cover 66 and from the cover 66 to the surroundingatmosphere.

While several embodiments of our invention have been shown and describedit will be apparent that other adaptations and modifications may be madewithout departing from the scope of the following claims.

We claim:

1. Apparatus for cooling heated strip which comprises vertically spacedrotatable rolls for supporting said strip, a cooling chamber betweensaid rolls throughout the majority of the distance between the rolls,means for supplying a cooling medium to the cooling chamber, and meansfor moving the peripheral surface of the strip in a non-circular pathWhile in contact with at least one of the rolls to rapidly vibrate thestrip in its passage between the rolls whereby heat transfer from thestrip is accelerated.

2. Apparatus for cooling heated strip according to claim 1 in which themeans for moving the strip in a noncircular path includes flutes in theperipheral surface of at least one of said rolls.

3. Apparatus for cooling heated strip according to claim 1 in which themeans for moving the strip in a non-circular path includes a frame forsupporting at least one of said rolls, a pivot support for said frame,and means for rapidly vibrating said support about its pivot.

References Cited in the file of this patent UNITED STATES PATENTS485,694 Haskell Nov. 8, 1892 1,765,955 von Maltitz et al June 24, 19302,326,163 Patterson Aug. 10, 1943 2,351,163 Thomas June 13, 19442,351,549 Schwartz June 13, 1944 2,393,243 Fanz Jan. 22, 1946 2,514,797Robinson July 11, 1950 2,572,484 Howle et a1. Oct. 23, 1951 2,613,070Verwohlt Oct. 7, 1952 2,645,031 Edwards July 14, 1953 FOREIGN PATENTS532,144 Great Britain Jan. 17, 1941

